Method of preventing dropped casing string with axial load sensor

A method of running casing into a well utilizes a load sensor to avoid dropping the casing string accidentally. The rig has a spider at the rig floor that suspends a casing string in the well when in a gripping position. A casing lifting mechanism will place a new joint of casing on the casing string suspended in the spider. The new joint of casing is rotated to make up with the casing string. After makeup, the casing lifting mechanism lifts the new joint of casing and the casing string. The operator releases the spider to allow the casing string to be lowered further into the well. Before releasing the spider, a load sensor will send a signal indicating that the casing lifting mechanism is supporting a minimum amount of weight.